JP6642606B2 - Cleaning method for membrane separation equipment - Google Patents

Description

  The present invention relates to a method for cleaning a membrane separation device used for water treatment, and in particular, to a method using a UF membrane (ultrafiltration membrane) or a MF membrane (microfiltration membrane) to suspend or disperse organic or inorganic colloids, The present invention relates to a method for effectively cleaning a membrane separation device (separation membrane device) from which inorganic dissolved substances have been separated and removed.

  In a membrane separation apparatus (a clarification membrane apparatus) using a UF membrane (ultrafiltration membrane) or an MF membrane (microfiltration membrane) for the purpose of turbidity, the dirt adheres to the separation membrane during filtration. The cleaning fluid (water and / or gas) is intermittently supplied to the raw water chamber or the permeated water chamber of the membrane module every 60 minutes of filtration time to physically clean the membrane.

  However, contamination that cannot be removed even by this physical cleaning accumulates on the surface of the film or in the film, so that the filtration ability of the film gradually decreases. In addition, when the raw water contains turbidity or when the device is operated with a high water recovery rate, solids such as turbidity accumulate in a cake between the membranes or between the membrane and the housing, and the effective membrane filtration area Decrease. Therefore, in the opaque membrane device, chemical cleaning using chemicals regularly or irregularly, and enhanced physical cleaning for the purpose of turbidity are required.

  For chemical cleaning, an acid agent (sulfuric acid, hydrochloric acid, nitric acid, citric acid, oxalic acid) or an alkali agent (sodium hydroxide), an oxidizing agent (sodium hypochlorite) and the like are generally used (Non-Patent Document 1). ), Which chemical to use depends on the material of the membrane and the fouling component of the membrane. In the enhanced physical cleaning, there is a method of vigorously blowing a cleaning fluid (water and / or gas) into the raw water chamber side of the membrane module for the purpose of vibrating the membrane, and applying ultrasonic waves (Non-Patent Document 2). The chemical cleaning and the enhanced physical cleaning are rarely used alone, and it is common to perform the cleaning combining the chemical cleaning and the enhanced physical cleaning over half a day to several days. In particular, when turbid contamination in which solids such as turbid solids accumulate on the film surface or the inside of the module occurs, the cleaning effect is insufficient with chemical cleaning alone, and therefore a combination with enhanced physical cleaning is essential.

  However, in the case of the opaque membrane device, when the membrane end is fixed to the module housing, even when the enhanced physical cleaning is performed, the membrane does not sufficiently vibrate, and a sufficient turbidity effect may not be obtained. . In particular, in the turbidity membrane device using the internal pressure type hollow fiber membrane module, since the raw water chamber is inside the hollow fiber membrane module having a diameter of about 1 mm, the turbid matter in the raw water chamber is hardly discharged out of the membrane module, and A physical cleaning method in which the membrane is shaken by blowing air into the raw water chamber cannot be used. For these reasons, the internal pressure type hollow fiber membrane module has a structure that easily causes turbid contamination, and it is difficult to clean the turbid contamination. Improvements in the cleaning method are desired.

  Surfactants are used as solvents or dispersants for raw material resins and pore-forming agents in the production process of separation membranes in membrane separation devices (Patent Document 1).

  In the operation process, a surfactant is rarely used for the purpose of cleaning the membrane separation device, but in Patent Document 2, the surfactant is used for cleaning the ultrapure water production device. Further, Patent Literature 3 describes a technique using an amphoteric surfactant for modifying the separation membrane so as to impart antibacterial properties. However, Patent Literatures 2 and 3 all aim at cleaning a turbidity membrane device. Not a technology.

  Patent Literature 4 discloses an example in which an amphoteric surfactant is used for cleaning a turbid membrane device. Patent Literature 4 describes use of the amphoteric surfactant as a detergent for a turbid membrane device in a food processing process. However, the cleaning liquid of Patent Document 4 is characterized by containing a phosphonate, a hypochlorite, an alkali agent, and a polymerized phosphate as essential active ingredients, and the amphoteric surfactant is an essential active ingredient. It is optionally added to the components. However, when phosphorus is used as a washing solution as in Patent Document 4, high concentration of phosphorus is contained in washing wastewater and filtered water of a turbidity membrane after washing, so that biofouling is performed during washing wastewater treatment and startup after washing. There is a concern that the risk of ringing increases. In addition, when the cleaning liquid contains an oxidizing agent, there is a problem that a large amount of flushing water and time are required because the post-stage apparatus is not deteriorated when water is passed after cleaning.

JP 2005-146230 A JP-A-2004-122020 JP 2009-112927 A JP 2012-106160 A

Shigeki Sawada, “Membrane Filtration Technology Useful in the Field” (2006) p120-121 Shigeki Sawada, “Membrane Filtration Technology Useful in the Field” (2006), p94-95

  An object of the present invention is to provide a cleaning method effective for turbid contamination even in a turbidity membrane device having an internal pressure type hollow fiber membrane module using a cleaning solution containing neither phosphorus nor an oxidizing agent.

As a result of repeated studies to solve the above problems, the present inventor has found that a cleaning solution containing an amphoteric surfactant and not containing phosphorus and an oxidizing agent can effectively clean turbid contamination of a separation membrane of a turbidity membrane device. It has been found that it can be removed.
That is, the present invention provides the following.

[1] A method for cleaning a membrane separation device including a membrane module in which the interior is partitioned into a raw water chamber and a permeated water chamber by a separation membrane, wherein the cleaning solution contains an amphoteric surfactant on the surface of the separation membrane on the raw water chamber side. A method for cleaning a membrane separation device, comprising a cleaning step of contacting the membrane.

[2] The method for cleaning a membrane separation device according to [1], wherein the cleaning solution contains 0.01 to 5% by weight of the amphoteric surfactant and does not contain phosphorus and an oxidizing agent.

[3] The membrane according to [1] or [2], comprising a step of drying the surface of the raw water chamber side membrane by bringing the raw water chamber into contact with air, and performing the washing step after the drying step. A method for cleaning the separation device.

[4] The cleaning step is one of a step of passing the cleaning solution from the permeated water chamber side of the membrane module to the raw water chamber side and a step of circulating the cleaning solution to the raw water chamber side of the membrane module. Alternatively, the method for cleaning a membrane separation device according to any one of [1] to [3], including both.

[5] The method for cleaning a membrane separation device according to any one of [1] to [4], wherein the membrane module is an internal pressure type hollow fiber membrane module.

According to the present invention, a cleaning solution containing an amphoteric surfactant is brought into contact with the membrane surface on the raw water chamber side, thereby effectively floating turbid contaminants on the membrane surface and discharging the same out of the system. A high cleaning effect can be obtained even in a turbidity membrane device having
Moreover, the cleaning solution of the present invention does not contain phosphorus or an oxidizing agent, and does not have the problem of biofouling or excessive flushing operation for discharging the oxidizing agent due to phosphorus.
In particular, in the present invention, prior to the washing step with the washing solution, a pretreatment for exposing the raw water chamber to the air to dry the surface of the raw water chamber-side membrane can provide a higher turbidity removing effect.

5 is a graph showing the results of Examples 1 and 2 and Comparative Examples 1 to 4. FIG. 10 is a configuration diagram illustrating an internal pressure type mini-module test device created in Example 3.

  Hereinafter, embodiments of the method for cleaning a membrane separation device of the present invention will be described in detail.

<Mechanism>
The cleaning effect of the cleaning solution containing the amphoteric surfactant in the cleaning method of the membrane separation device of the present invention and the effect of the drying operation before cleaning are considered as follows.

The surfactant infiltrates the inside of the turbid contaminant by its permeation action, and has an effect of being removed from the membrane surface by emulsification and dispersion action. In particular, since the amphoteric surfactant has both an anion and a cationic group in the hydrophilic part in the molecule, the bonding between adjacent amphoteric surfactant molecules becomes strong and dense. As a result, micelles formed with an amphoteric surfactant disintegrate micelles while turbidity is encapsulated in the micelles, compared to micelles formed with a positive, negative, or nonionic surfactant. It is easy to discharge out of the system without the need.
In addition, by drying the raw water side membrane surface, the cake-like turbid contamination adhering to the membrane surface is dried and shrunk, causing a gap between the turbid contamination and the membrane surface, or forming a crack between the turbid contamination. This can increase the contact area between the turbid substance and the washing solution, thereby obtaining an effect that the turbid substance is easily lifted from the membrane surface.

<Cleaning solution>
In the present invention, examples of the amphoteric surfactant used as an active ingredient of the washing solution include an amino acid type amphoteric surfactant [higher alkyl (C12 to C18) sodium aminopropionate and the like] and a betaine type amphoteric surfactant [alkyl ( C12 to C18 dimethyl betaine, alkyl (C12 to C18) dihydroxyethyl betaine, etc.], sulfate ester type amphoteric surfactant [Sulfur ester of higher alkyl (C8 to C18) amine sodium salt, hydroxyethyl And sodium sulfonate-type amphoteric surfactants (such as pentadecylsulfotaurine and imidazolinesulfonic acid). These may be used alone or in combination of two or more. Of these, betaine-type amphoteric surfactants are preferred.

  The content of the amphoteric surfactant in the washing solution is preferably 0.01% by weight or more, particularly preferably 0.5% by weight or more. If the content of the amphoteric surfactant is too small, a sufficient cleaning effect may not be obtained. The upper limit of the content of the amphoteric surfactant in the cleaning solution is not particularly limited because it is attributable to the micelle concentration of the amphoteric surfactant. It is preferable that the content be 5% by weight or less, since the flushing water and time may be increased.

It is important that the cleaning solution of the present invention is basically free of other components, particularly phosphorus and an oxidizing agent, as an aqueous solution of an amphoteric surfactant.
Further, the pH of the washing solution used in the present invention is preferably 11 or more, particularly preferably about 12 to 13 in terms of the effect of removing and removing turbidity. It may contain an alkali agent such as potassium oxide.

  In particular, the washing solution used in the present invention is preferably a washing solution containing an amphoteric surfactant having a concentration of 1 to 5% by weight under strong alkaline conditions of pH 13 or more.

<Washing process>
In the present invention, the separation membrane is washed by bringing a washing solution containing an amphoteric surfactant into contact with the surface of the membrane on the side of the raw water chamber of the membrane module in which the inside is separated into the raw water chamber and the permeated water chamber by the separation membrane. Specifically, this washing step is preferably performed by the following steps (1) and / or (2).
(1) The step of passing the cleaning solution from the permeated water chamber side of the membrane module to the raw water chamber side (2) The step of circulating the cleaning solution to the raw water chamber side of the membrane module The steps (1) and (2) are performed When performing, any of them may be performed first, but it is more preferable to perform the step (1) first. By performing the step (1) first and then performing the step (2), it is possible to remove the turbid contamination on the membrane surface and then to hydrophilize the surface of the raw water chamber side membrane. Since the contact efficiency of the surface is improved, the hydrophilic treatment can be performed in a short time. The steps (1) and (2) may be repeated alternately.

  Cleaning conditions such as the cleaning time and the flow rate of the cleaning solution also vary depending on the amphoteric surfactant concentration and pH of the cleaning solution to be used and the degree of contamination of the separation membrane to be cleaned. Just set it.

  After washing, it is preferable to perform flushing according to a conventional method.

<Drying process>
In the present invention, prior to the above-described washing step, it is preferable to perform a drying step of drying the raw water chamber side membrane surface by bringing the raw water chamber of the membrane module into contact with air, and by performing this drying step, An even higher turbidity removing effect can be obtained.

  The specific method of the drying step is not particularly limited, and a method of blowing compressed air into the raw water chamber side of the membrane module, or allowing the membrane module to stand still so as to come into contact with the outside air can be adopted.

<Membrane module>
There is no particular limitation on the membrane separation apparatus to be cleaned by the method for cleaning a membrane separation apparatus of the present invention.・ Effective for cleaning UF and MF membranes in turbidity membrane devices used to separate and remove inorganic colloids, organic and inorganic dissolved substances, etc. Of these, turbid substances in the raw water chamber are particularly difficult to be discharged out of the module Also, it is suitable for removing turbidity of an internal pressure type hollow fiber module to which a physical cleaning method is difficult to apply.

  Hereinafter, the present invention will be described more specifically with reference to examples.

  The surfactants used in the following Examples and Comparative Examples are as follows.

<Amphoteric surfactant>
Double-sided surfactant A: "Lebon CIB" (alkyl carboxymethyl hydroxyethyl imidazolium betaine represented by the following structural formula) manufactured by Sanyo Chemical Industries, Ltd.

  Amphoteric surfactant B: "LEBON MY-30" (manufactured by Sanyo Kasei Kogyo Co., Ltd.) (amidopropyl betaine mistyrylate represented by the following structural formula)

<Nonionic surfactant>
Nonionic surfactant A: "Naroacty ID-40" (polyoxyethylene alkyl ether) manufactured by Sanyo Chemical Industries, Ltd.
Nonionic surfactant B: "Naroacty ID-60" (polyoxyethylene alkyl ether) manufactured by Sanyo Chemical Industries, Ltd.

<Negative surfactant>
Negative surfactant A: “Sandet EN” (Sodium polyoxyethylene alkyl ether sulfate) manufactured by Sanyo Chemical Industries, Ltd.

[Examples 1 and 2, Comparative Examples 1 to 4]
The cleaning effect of the turbid matter derived from the liquid crystal factory effluent was examined by the following cleaning test.
(1) Water from a liquid crystal plant was passed through an MF membrane having a pore size of 0.45 μm to form an MF contaminated membrane.
(2) 10 mL of pure water was passed through the MF-contaminated membrane, and the time T0 required for passing water was determined.
(3) The MF-contaminated membrane was immersed in the cleaning solution for 3 minutes, and thereafter, 10 mL of pure water was passed through, and the time T1 required for passing water was determined.
The cleaning solutions shown in Table 1 were used. The blank of Comparative Example 1 was water adjusted to pH 12 with NaOH, and the other was prepared by dissolving each surfactant at a concentration of 1% by weight and adjusting the pH to 12 with NaOH.
(4) The above-mentioned (1) to (3) were performed for three samples of the MF-contaminated membrane having a variation in T0 by changing the amount of drainage passing through the MF membrane.
(5) The horizontal axis T0 and the vertical axis T1 were plotted, and the cleaning effect was evaluated by the slope T1 / T0 derived from the test results at three points.
That is, it was determined that the larger T1 / T0, the lower the cleaning effect, and the smaller T1 / T0, the higher the cleaning effect.

  The results are shown in Table 1 and FIG.

  From Table 1 and FIG. 1, it can be seen that the cleaning effect is amphoteric surfactant> negative surfactant ＞ nonionic surfactant> blank, and that the amphoteric surfactant exhibits the best cleaning effect.

[Example 3]
Take out the hollow fiber membrane from the internal pressure type hollow fiber membrane module (hollow fiber UF membrane, pore diameter 0.03 μm, membrane inner diameter 0.9 mm, membrane material polyether sulfone) contaminated in the liquid crystal plant wastewater recovery facility, and wash it by the following procedure The test was performed.
As the washing solution, a solution prepared by dissolving the amphoteric surfactant A in water at a concentration of 1% by weight and adjusting the pH to 13 with NaOH was used.
(1) An internal pressure type mini-module test device (film length 7.5 cm, area 10.6 cm ² ) shown in FIGS. 2A and 2B was prepared using the five contaminant films.
In FIG. 2 (a), 1 is a contaminated hollow fiber membrane, 2 is a potting agent, 3 is a permeated water outlet, 4 is a module housing, and five hollow fiber membranes 1 are loaded inside.
Raw water was introduced into the membrane from both ends of the hollow fiber membrane 1, and permeated water that had passed through the membrane was taken out from the outlet 3.
As shown in FIG. 2B, pipes were connected to the internal pressure mini-module 10 to obtain an internal pressure mini-module test apparatus. In this test apparatus, by opening the valves V ₁ and V ₄ and closing the valves V ₂ and V ₃ , air can be introduced into the hollow fiber membrane 1 from the pipes 11, 12 and 13. Moreover, by operating the pump P, and valve _{V 3} is opened, be a cleaning solution cleaning solution tank 5 the valve _{V 1, V 2, V 4} by the closed circulating pipe 14,12,13 it can. 6 is a permeate tank.
(2) Compressed air of 0.15 MPa was passed through the raw water chamber for one hour to dry the membrane.
(3) The washed solution raw water chamber side circulated for 6 hours, then the cleaning solution the cleaning solution tank 5 replaced with pure water, to actuate the pump P, and the valve V ₄ opened, the valve V _1, V ₂ , by the V ₃ is closed, after enough flushing hollow fiber membrane 1 with pure water to remove the cleaning solution.
(4) Permeability of the new film before the test, the contamination membranes and membrane after washing before washing, the pump P is operated, the valve V ₂ opens, the a closing valve V _1, V _3, V ₄ Then, the pure water equivalent to ² m ³ / m ² / d in flux (permeation flux) is fed into the hollow fiber membrane 1 so as to completely filter the pure water, and the pressure at this time is measured with a pressure gauge PI to obtain a new membrane. The water permeability of each of the contaminated membrane before washing and the membrane after washing (permeation flux when converted to an operating pressure of 1 bar, unit: lmh) was calculated, and the water permeability recovery rate was calculated from the following equation.
Permeability recovery rate (%)
= Water permeability after washing [lmh] / water permeability of new membrane [lmh] x 100
Table 2 shows the results.

[Example 4]
A cleaning test was performed in the same manner as in Example 3 except that the step (2) was omitted, and the results are shown in Table 2.

From Table 2, the water permeability recovery rate of Example 4 washed without drying was about 30%, whereas the water permeability recovery rate of Example 3 dried before washing was 99%. It can be seen that the washing effect was significantly improved by drying.
This is considered to be due to the fact that the turbid contaminants fixed to the film surface due to the drying were dried and shrunk, so that they were easily peeled off from the film, and the washing effect of the amphoteric surfactant was increased.

DESCRIPTION OF SYMBOLS 1 Hollow fiber membrane 2 Potting agent 3 Permeate outlet 4 Module housing 5 Cleaning solution tank 6 Permeate tank 10 Internal pressure type hollow fiber mini module

Claims (4)

A method for cleaning a membrane separation device including a membrane module in which the interior is partitioned into a raw water chamber and a permeated water chamber by a separation membrane, wherein the separation membrane contains an amphoteric surfactant on the surface of the raw water chamber side membrane, and has a pH of 11 to 13. A washing step of contacting an alkaline washing solution, and a drying step of drying the raw water chamber side membrane surface by bringing the raw water chamber into contact with air, and performing the washing step after the drying step. A method for cleaning a membrane separation device including: The cleaning solution contains 0.01 to 5% by weight of the amphoteric surfactant, wherein the amphoteric surfactant is alkylcarboxymethylhydroxyethyl imidazolium betaine and / or amidopropyl betaine mystyrylate, and The method for cleaning a membrane separation device according to claim 1, wherein the method does not contain an agent. The cleaning step includes passing one or both of a step of passing the cleaning solution from the permeated water chamber side of the membrane module to the raw water chamber side and a step of circulating the cleaning solution through the raw water chamber side of the membrane module. including, cleaning method of the membrane separation apparatus according to claim 1 or 2. The method for cleaning a membrane separation device according to any one of claims 1 to 3 , wherein the membrane module is a hollow fiber membrane module of an internal pressure type of a contaminated membrane through which liquid crystal plant wastewater is passed .

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